Method of laundering



Jan. 10, 1939. A, EKSTRMV 2,143,307

METHOD OF LAUNDERING Filed Nov. 3, 1936 2 SheetsPSheet l r fo 3a da 5| 60? 70 vastly; A/ca//be :oop Joh/him 1,

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Jan. l0, 1939.

A. EKSTRM METHOD 0F LAUNDERING Filed Nov. 3, 1936 2 Sheets-Sheet 2 Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE Application November 3, 1936, Serial No. 109,032 In Sweden November 13, 1935 3Claims.

This invention relates to an improved method of washing clothes by means of alkaline soap solutions in laundries.

The chief object of the invention is to avoid the drawbacks in the washing methods hitherto generally used and to attain a more perfect removal of the dirt particles with less work and in a shorter time than hitherto was possible.

Another object is to recover the chief part of the washing lye in such form that it can be again used in a subsequent washing operation.

A further object is to render it possible to use a washing solution of substantially constant composition for washing clothes of different textile materials and diilerent degrees of dirtiness so that such washing solution can be prepared outside the laundry machines in a tank common to a plurality of laundry machines and from said tank be supplied to the laundry machines in a quantity required for each washing operation to be performed in said machines.

A further object is to facilitate the rinsing of the washing lye from the washed clothes and or to reduce the wear on the clothes during the rinsing operation.

In the accompanying drawings Figs. l and 2 are diagrams illustrating washing methods now in use in laundry plants. In Fig. 3 I have shown n dlagrammatically a laundering plant according "n to my invention.

In laundering plants now in use the washing is generally performed in laundering machines consisting of a stationary drum with an inner mi perforated rotary cylinder which is charged with the dirty clothes, the soaking of the clothes as well as the washing and rinsing being performed in said apparatus. A usual performance of a washing operation. is illustrated by the diagram shown in Fig. 1. The abscissas indicate the time 40 while the ordinates indicate by the full line the liquid quantities used and by the dotted line the temperature. The dirty clothes are rst soaked in clear water or a weak soap solution in the machine for about 7 .to 8 minutes while using 4" a quantity of liquid amounting to about ten times the weight oi' the clothes, thus for instance about 500 l. of water to 50 kgs. of clothes. The temperatlne during the soaking is raised to about C. After the soaking the of 5 wnteradnwnommewarremaimngmme clothesamountlngtoabout3timestheweight oftheclcthesfl'henpurewatm'issuppliedso thattbetotalquantityofwateramountstoabout 4timestheweightoftheclothesandfurtbsra detergent. generally a rather concentrated lllrinsing operation.

tion oi' soap and carbonate of soda or caustic soda. is added. The washing then takes place with the lye thus formed in the machine for about'40 minutes, the rtemperature being successively raised during this operation by a supply 5 of steam to about 80 to 90 C. During this operation the washing cylinder is continuously rotated or oscillated. Then the excess 'of the dirty lye is drawn oil. On account of the porosity of the clothes about of the dirty lye is retained by 10 the clothes and must be removed by rinsing. For such purpose the lye retained by the clothes is diluted by fresh water while maintaining the rotation of the machine, whereupon the excess of liquid is again drawn oil'. This rinsing opera- 5 tion is repeated 5 to 7 times with a successively increased quantity of water. whereupon the clothes are practically free from the dirty lye. During the rinsing operation the temperature is successively lowered to thel temperature of the rinsing water supplied.

The diiliculties in a laundering operation as above described are especially prominentin the In the rst rinsing step it is necessary to avoid such dilution of the dirty lye 95 that the dirt particles emulsied by the soap are precipitated on the clothes. Furthermore. if the washing water used is not absolutely soft lime soap and other insoluble soaps and calcium carbonate are formed in the washing operation 30 as well as in the rinsing operation. The insoluble soaps absorb easily dirt particles from the dirty lye and when they precipitate on the washed clothes the latter will get a grayish tint.

In order toY avoid the accumulation of dirty partic1es.and insoluble soaps in the washing lye it is known to carry out the washing and rinsing operations in the manner illustrated by the diagram in Fig. 2. According to said method the dirty lye is partly drawn ci! several times during the washing operation and fresh washing solu-` tion is supplied as is illustrated in Fig. 2 by the full line between the soaking-and the rinsing operations, said line showing three successive regenerations of the soap solution used by d rawing of! dirty lye and supplying corresponding quantities of fresh alkaline soap solution. In thismanner an improved washing is obtained and the subsequent rinsing is facilitatedbut the value of the method isreduced by the fact that the greater part of the dirty lye is retained b! theclothessothattheregenerationofthe Illn'tlmwmv re. thcrepea of drawing on dirty 17e and 8WD!!- !ng fresh lye during the washing operation in creases the work of the workers and also the consumption of soap and alkali is increased.

According to my invention, the chief object of which is to avoid the drawbacks of the said known Washing operations, the washing lye is continuously freed from insoluble soaps formed during the washing operation as well as from fat and dirt particles emulsied in the washing lye by being continuously centrifuged outside the laundering machine. The centrifuging is carried out by means of a centrifugal sludge separator of well-known construction, through which the washing lye is circulated and in which any particles of a specific gravity different from that of the lye are deposited. In the Washing operation the fat contained in the clothes as well as dirt particles is emulsiiled in the soap solution and as the fat particles are lighter than the lye they will move towards the center of the separator drum where they deposit while the insoluble soaps and dirt particles which are heavier than the lye deposit on the internal wall of the separator drum. The washing lye is thereby practically free from insoluble matters at the end of the washing operation. The lye drawn off before the rinsing of the clothes takes place is collected for use in a subsequent washing operation. Also the rinsing water rst drawn off in the rinsing operation which still is rich in soap and alkali is recovered for use in a subsequent washing operation, only a small quantity of soap and alkali being required to bring its strength up to the proper value. The rinsing operation is then, preferably, performed by a continuous supply of fresh Water which successively removes the washing lye absorbed by the clothes until the latter are practically free from soap and alkali.

In the washing methods hitherto used it is necessary for obtaining a good washing result to adjust the content of detergents in the lye according to the degree of dirtiness of the clothes and for economical reasons the quantity of washing lye should not exceed what is absolutely necessary. Such adjustment of the strength of the washing lye generally takes place for each charge of clothes to be washed after an estimation of its content of fat and dirt by adding variable quantities of detergents to the washing water used in the laundering machine. Too high a percentage oi' alkali can in such case be detrimental to the clothes. According to my washing method in which the washing lye as above described is continuously purified from insoluble matters, it is not necessary to adjust the strength of the washing lye according to the degree of dirtiness of the clothes but a quite satisfactory result is obtained' by means of a washing lye of constant composition, the percentage of soap and alkali being adjusted in such manner that it does not injure the clothes. Such washing lye is, preferably, prepared in a storage tank which is common to a plurality of laundering machines and to which the washing lye used and also the rinsing water rich in soap is returned after having been clarified by centrifuging. As the rinsing water collected successively dilutes the lye in the storage tank an addition of detergents to the tank must be made to maintain its strength substantially constant. rThe quantity of rinsing water collected is, preferably, adjusted in such manner that it corresponds to the loss of washing lye in the washing operation. If a less quantity of rinsing water is recovered the required additional lye is prepared from fresh water and detergents.

As the excess of the washing lye used is always returned to the storage tank it does not mean any loss if an ample quantity of Washing lye is used in the laundering machines but the washing is facilitated in such manner and the wear on the clothes is reduced. My improved method also essentially simplifies the managing of the laundering machines and the washing operation. A reliable continuous control over the composition of the Washing lye used in the laundry can easily be obtained by testing the lye in the storage tank. The soap content of the lye can according to the circumstances vary from 3 to 8 g. and the alkali content from 2 to 5 g. sodium carbonateror l to 3 g.' sodium hydroxide per liter. A high percentage of soap reduces the wear on the clothes, the upper limit being given only by the necessity of avoiding foaming in the laundering machines. The alkali content in the lye facilitates the Washing, for insta-nce by partly saponifying the fat contained in the clothes but on the other hand it has an unfavorable action in this that the alkali is to a great extent aolsorbed in the textile fibres of the clothes whereby its removal in the rinsing operation is rendered difficult. It is usual, therefore, in washing clothes with a solution of soap and alkali to add an acid or an acid salt towards the end of the rinsing operation in order to neutralize the alkali which has not been removed by the rinsing water and thus prevent the textile fibres from being injured by remaining alkali. According to my invention the rinsing operation is highly facilitated by performing the neutralization of the alkali at the end of the washing operation but before the rinsing or in connection with the first rinsing bath. As neutralizing agent any acid or any other substance of acid character which is not injurious to the clothes may be used but I prefer to use sodium bisulphite. In many cases the neutralization may be effected by means of a saponiiiable fatty acid, which reacts with the alkali to form soap. The quantity of neutralizing agent should be adjusted in such manner that a precipitation of free fatty acid on the clothes does not take place. I have found that on neutralizing to a pH value of 9 to ll such drawback is avoided and the effect is attained that the clothes already at the beginning of the rinsing operation only are holding a small percentage of alkali adsorbed. the rinsing being, therefore, easily performed after such neutralization.

In order to avoid the dilution of' the washing lye by condensed water formed in the heating of the lye by means of steam I prefer to use indirect heating oi' the washing lye, said heating being, preferably, carried out in such manner that a liquid heating apparatus heated by pressure steam is provided in the circulating conduit -between the centrifugal sludge separator and the laundering machine. As the washing liquid passing through said heating apparatus is free from insoluble soaps and other solid particles the heating apparatus will remain free from deposits 01' solid matters which otherwise would disturb the continuous working.

In Fig. 3 I have shown diagrammatically an embodiment of a laundering plant operated ac` cording to my invention. For the sake of sim- -plicity only one laundering machine with its centrifugal sludge separator has been shown but it is to be understood that generally a plurality of such aggregates is used in the plant which are connected in parallel to the common storage tank for the washing lye.

Referring to lllg. 3, I is a laundering machine' of any well-known design which by means of a conduit 2 is connected to a tank 3 containing an alkaline soap solution used as washing liquid. The tank 3 is, preferably, divided into two compartments which are used in such manner that the washing liquid required for the washing operations is taken from one compartment while used washing liquid and rinsing water rich in soap after centrifuging are being collected in the other compartment. To the laundering machine is connected a circulation conduit I containing a pump 6 for the circulation of the wash ing liquid, a centrifugal sludge separator Il for removing insoluble particles from the washing liquid, and a liquid heating apparatus l for the successive heating of the washing lye during the washing operation. By means of a three-way cock 8 and a conduit 3 the washing liquid drawn of! from the laundering machine and purified by the separator is returned to the storage tank 3. 'I'he laundering machine is further provided with a supply pipe I and an outlet pipe Il for rinsing water. The heating apparatus 1 is provided with a steam inlet I2 and an outlet I3 for condensed water.

'I'he operation of the plant above described is as follows. The clothes are charged in the laundering machine together with the required quantity of washing liquid from the tank 3. The laundering machine i as well as the pump 5 and the separator 3 are then started, the cock il being in such position that the circulating lye is returned from the separator through the heating apparatus l to the laundering machine. Steam is supplied during the circulation to the heating apparatus 1 so that the washing lye is successively heated to a temperature of 80 to 90 C. The circulating washing lye is purified in the separator 8 from insoluble soaps formed during the washing and from fat and dirt particles removed from the clothes so that the washing lye remains practically free from insoluble matters during the whole washing operation. After the clothes` have been cleansed the cock 8 is reversed so that the excess of washing liquid is returnedtothetank3throughthepump5,the separator 8 and the conduit 3. Rinsing water is then supplied to the machine I through the conduit lli and mixed with the lye absorbed in the clothes so that a diluted soap solution is obtained in the machine. The excess of said solutionislikewisedrawnoifthroughthepumpl.

theseparatorandtheconduitltothetankl. Before or simultaneously with the supply of the nrst rinsing water a neutralizing agent, for instance sodium bisulphite, is supplied to the laundering machine in such quantity that the washing lye is neutralised topa pH value of 9 to 11. After the drawing oil' of the first rinsing water, the pump l is stopped, whereupon more rinsing water ls supplied to the machine I through the pipe Ill, the excess flowing oil through the pipe Il until the clothes are practically free from soap and alkali.

The sludge collected in the separator which consists partly of fat deposited at the centre of the centrifugal drum, and insoluble soaps and dirt particles deposited at' the periphery of the drum are removed at suitable intervals when the circulation is stopped. The content of soap and alkallofthelyecollectedinthetank3isadjusted to the proper value by adding soap or fatty acid and alkali until the desired strength is attained whereupon the lye is ready for continued use. Its degree of purity remains practically the same as that of a washing liquid freshly prepared from pure water and detergents.

What I claim is:

1. The method of washing clothes which comprises immersing clothes in a body of alkaline soap solution, continually drawing oil! soap solution from the washing body during the washing operation, separately removing fat and dirt particles from the solution drawn ofi' by subjecting it to a centrifugal separating process, and then returning the purified solution to the washing body.

2. In a method as claimed in claim l the additional steps oi' separating the chief part of the purified body of wash solution from the clothes after finishing of the washing operation, rinsing the washed clothes by supplying fresh water. withdrawing the rinse water, purifying the rinse water rich in soap by subjecting it to a centrifugal separating process, and collecting the rinse water thus purined together with the puriiled washing solution.

3. In a method as claimed in claim 1 the additional step of reducing the alkalinity of the soap solution to a pli-value of about 9 to 11 at the end od the washing operation to facilitate the removal of the alkali adsorbed to the textile libres of the clothes in performing the rinsing of the clothes.

AIJ'RED EKBTRM. 

